elasticsearch - discovery.zen.minimum_master_nodes value for a cluster of two nodes -

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i have 2 dedicated windows servers (windows server 2012r2, 128gb memory on each server) es (2.2.0). if have 1 node on each server , 2 nodes form cluster. proper value 

discovery.zen.minimum_master_nodes

i read general rule in elasticsearch.yml:

prevent "split brain" configuring majority of nodes (total number of nodes / 2 + 1):

i saw thread:

proper value of es_heap_size dedicated machine 2 nodes in cluster

there answer saying:

as described in elasticsearch pre-flight checklist, can set discovery.zen.minimum_master_nodes @ least (n/2)+1 on clusters n > 2 nodes.

please note "n > 2". proper value in case?

n number of es nodes (not physical machines es processes) can part of cluster.

in case, 1 node on 2 machines, n = 2 (note 4 here), formula n/2 + 1 yields 2, means both of nodes must eligible master nodes if want prevent split brain situations.

if set value 1 (which default value!) , experience networking issues , both of nodes can see each other brief moment, each node think alone in cluster , both elect master. end in situation have 2 masters , that's not thing. whereas if set value 2 , experience networking issues, current master node stay elected , second node never decide elect new master. whenever network up, second node rejoin cluster , continue serving requests.

the ideal topology have 3 dedicated master nodes (i.e. master: true , data:false) , have discovery.zen.minimum_master_nodes set 2. way you'll never have change setting whatever number of data nodes part of cluster.

so n > 2 constraint should indeed n >= 2, guess somehow implied, because otherwise you're creating fertile ground split brain situations.


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